U.S. patent number 5,137,769 [Application Number 07/625,503] was granted by the patent office on 1992-08-11 for vibration dampening means for strung or spoked equipment.
This patent grant is currently assigned to Supracor Systems, Inc.. Invention is credited to Curtis L. Landi.
United States Patent |
5,137,769 |
Landi |
August 11, 1992 |
Vibration dampening means for strung or spoked equipment
Abstract
Means for dampening vibrations in a strung game racket or a
spoked wheel comprising a block of flexible, thermoplastic
elastomer honeycomb bonded to and sandwiched between two
thermoplastic facings. The device is inserted between at least two
strings of the interwoven string diaphragm of the racket, or two
spokes in a spoked wheel arrangement, in such a manner as to allow
the exposed honeycomb core at the sides of the device to wrap
around the engaged strings or spokes and hold the device in place.
The device absorbs vibrations in the strings that originate from
the striking surface when a ball is struck, and vibrations in the
spokes emanating from normal use of a wheel.
Inventors: |
Landi; Curtis L. (Mountain
View, CA) |
Assignee: |
Supracor Systems, Inc.
(Sunnyvale, CA)
|
Family
ID: |
24506395 |
Appl.
No.: |
07/625,503 |
Filed: |
December 11, 1990 |
Current U.S.
Class: |
428/116; 428/72;
473/522; 473/553; 428/118 |
Current CPC
Class: |
B32B
3/12 (20130101); F16F 15/073 (20130101); A63B
60/54 (20151001); B32B 27/06 (20130101); B32B
7/12 (20130101); B32B 27/08 (20130101); B32B
3/30 (20130101); F16F 7/00 (20130101); B32B
2274/00 (20130101); Y10T 428/234 (20150115); Y10T
428/24149 (20150115); Y10T 428/24165 (20150115); B32B
2307/56 (20130101); B32B 2305/024 (20130101); B32B
2250/40 (20130101); B32B 2307/5825 (20130101) |
Current International
Class: |
B32B
3/12 (20060101); F16F 15/06 (20060101); F16F
15/073 (20060101); A63B 59/00 (20060101); F16F
7/00 (20060101); B32B 003/12 () |
Field of
Search: |
;273/73C,73D,73F,73H,73J,75,81R,67A,73K
;428/116,118,71,72,73,37 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Robinson; Ellis P.
Assistant Examiner: Ahmad; Nasser
Attorney, Agent or Firm: Rosemblum, Parish & Issacs
Claims
What is claimed is:
1. Tear resistant, light weight vibration dampening means having a
width larger than the distance between two parallel rigid members
of strung or spoked equipment and severed from a body of material
comprising:
a flexible thermoplastic elastomeric core made from strips of
resilient thermoplastic elastomeric sheet material bonded together
to from the walls of a honeycomb network of generally hexagonally
shaped cells, said strips of material forming double thickness
walls at the locations where said strips are bonded together, the
walls of said cells each having upper edges and lower edges;
and
first and second sheets of resilient thermoplastic elastomeric and
flat facing material, thermal compression bonded to the upper and
lower surfaces of said core formed by said upper and lower edges,
hermetically sealed to encapsulate air in said cells;
wherein said dampening means is severed from said body of material
such that the severance along at least two sides is made normal to
said double thickness walls and proximate the midpoint of the
intersected double thickness walls to expose the edges of the walls
of each cell through which a severance is made, creating a
plurality of outwardly extending vertical ribs intermittently
spaced around the perimeter of said vibration dampening means.
2. Vibration dampening means as recited in claim 1 wherein
severance along at least two sides is made parallel to and
non-intersecting said double thickness walls, such that severance
along all sides maximizes the exposure of said vertical ribs.
3. Vibration dampening means as recited in claim 2 wherein said
plurality of vertical ribs are collapsible around a rigid member
when said rigid member is pressed against said ribs in a direction
normal to said vertical ribs.
4. Vibration dampening means as recited in claim 3 wherein each
sheet of said facing material bends toward the other at the
intersection of said facing with said vertical ribs when said rigid
member is pressed against said ribs causing said vertical ribs to
collapse.
5. Vibration dampening means as recited in claim 1 wherein said
core material is a resilient thermoplastic elastomer of a first
thickness and said facing material is a resilient thermoplastic
elastomer of a second thickness greater than said first
thickness.
6. Vibration dampening means as recited in claim 1 or 4 wherein
said rigid member is a first and second string of an interwoven
string diaphragm on a game racket.
7. Vibration dampening means as recited in claim 6 wherein said
first and second string are parallel to each other and in line.
8. Vibration dampening means as recited in claim 7 wherein said
dampening means also interfaces with a third string, disposed
perpendicular to said first and second parallel strings.
9. Vibration dampening means as recited in claim 8 wherein said
dampening means also interfaces with a fourth string, parallel to
said third string.
10. Vibration dampening means as recited in claim 1 or 4 wherein
said rigid member is a first and second spoke of a bicycle wheel.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to devices for dampening
vibration, and more particularly to a device that, when inserted
between a set of strings of a game racket, will dampen the
vibrations experienced by the strings (and the player) when the
strings contact a game ball. Additionally, the device may be
inserted between the spokes of a bicycle wheel such that vibrations
experienced by the wheel during use will be dampened before
reaching the frame of the bicycle.
2. Brief Description of the Prior Art
In strung, hand held game rackets, vibrations are produced when the
player causes the racket to strike a ball. These vibrations begin
in the area of the interwoven string diaphragm where the ball is
struck (the striking surface), radiate outwardly through the string
network to the frame of the racket, and then on to the hand and arm
of the player. Exposure to vibrations over a long period of time
can cause injury to the player's hand, wrist and arm. To avoid this
type of injury, it is desirable to reduce such string vibrations
before they reach the racket frame.
Early efforts to dampen vibrations were directed to the racket's
construction. Carbon and graphite racket frames replaced the
traditional wood frames, and the shape of the racket frame was
experimentally modified. Yet none of these changes amply reduced
the vibrations felt by the player. Natural catgut used for the
racket's strings was found to produce lower levels of vibration
than plastic strings, but players preferred the higher performance
plastic strings which, unfortunately, produce a higher level of
vibration.
After the early efforts to reconstruct the racket had failed,
inventors created shock absorbing inserts to be placed between a
set of strings for dampening vibrations. The vibration dampening
inserts in the prior art recognized that mechanically coupling or
mechanically isolating a set of strings by inserting a vibration
absorbing material between them, resulted in a dampening of the
vibrations that flow through the strings when the striking surface
of the racket hits a ball.
U.S. Pat. No. 4,180,265 involves a dampening device that couples
two parallel strings or one longitudinal string and one transverse
string together. The length of the device is smaller than the
distance between the strings, causing the distance between the
strings to be slightly reduced at the dampening device. The
vibration from the strings is dampened because the coupled strings
are detuned relative to each other and also because the elastomeric
material that the device is made from has inherent viscoelastic
dampening properties. This type of device is usually an integral
part of a racket. Therefore, it must be woven into the string
diaphragm at the time the racket is manufactured.
Converse to the mechanical couple, U.S. Pat. No. 4,609,194
illustrates a vibration dampening device that, when inserted
between a set of strings within a racket frame, mechanically
isolates the strings and absorbs the vibrations flowing through the
string diaphragm when a ball is hit. This is achieved by inserting
a compressed block of viscoelastic foam between two parallel
longitudinal strings and at least one adjacent transverse string,
and then releasing the foam block, allowing it to expand to its
natural shape. The expanded foam presses outwardly on the engaged
strings urging them away from one another, thus mechanically
isolating them. When vibration is produced in the striking surface
of the racket, the foam from which the device is made absorbs the
vibrations and turns the mechanical vibrational energy into heat
energy which is dissipated.
After insertion, the foam block expands in all directions where it
is unrestrained by the racket strings. The majority of the foam
expands in a direction generally normal to the direction of the
strings, causing an interruption in the flat plane of the racket
face that is created by the interwoven string diaphragm. When a
player swings the racket and hits a ball at the point on the
interwoven string diaphragm where this type of device is inserted,
the device will interfere with the normal travel of the ball and
misdirect the struck ball, thereby hampering the player's skill.
Additionally, these foam devices are rapidly destroyed under normal
wear and tear.
The spokes of a bicycle wheel experience vibrations during use
similar to the vibrating strings of a game racket. The spoke
vibrations from the front wheels are transmitted to the front forks
of the bicycle frame and then on to the main frame of the bicycle.
These vibrations affect the rider's arms as they continue through
the frame onto the handlebars. Further, the vibrations from the
rear wheel passes through the rear forks to the seat of the bicycle
causing the rider further discomfort.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide
vibration dampening means for a strung game racket comprising a
device having block of flexible, thermoplastic elastomer honeycomb
as its core and two sheets of resilient facing bonded thereto.
Another objective of the present invention is to provide superior
vibration dampening means for a strung game racket by placing a
block of flexible honeycomb between two parallel strings of the
racket's interwoven string diaphragm.
Briefly, a preferred embodiment of the present invention includes a
device comprising a block of flexible, thermoplastic elastomer
honeycomb bonded to and disposed between two thermoplastic facings.
The core of the device is made from a plurality of advanced grade,
thermoplastic elastomeric sheets that form a honeycomb-like network
of cells.
While the core is held in an expanded disposition, resilient
thermoplastic facings are fusion bonded to each surface. The
addition of the facings encapsulates air within each cell. Thus,
the preferred embodiment of a device of the present invention has a
flexible honeycomb core sandwiched between facings on the upper and
lower surfaces of the core. Since the facings are only on the upper
and lower surfaces, the core is exposed at the sides of the
device.
To dampen string vibration, the device is usually inserted into the
area between two parallel longitudinal strings, the first
transverse string and the racket frame, such that the facings of
the device are parallel to the plane of the interwoven string
diaphragm of the racket. Because the device is slightly larger than
the area between two parallel strings, the flexible cell material
wraps around the two parallel strings and holds the device in
place. Alternatively, or in addition, the device may be inserted at
any point or points around the racket frame. Further, the device
can be placed between the strings so that the sheets of
thermoplastic material are disposed in a horizontal direction along
the plane of the interwoven string diaphragm, or the device may be
installed so that the sheets are disposed ninety degrees thereto,
in a vertical direction.
An important advantage of the present invention is that the device
is made of thermoplastic and thermoplastic elastomeric materials
which absorb energy.
Another advantage of the present invention is that the device has
exceptional spring-back recovery characteristics due in part to the
materials used in its construction and in part to the encapsulated
air.
A further advantage of the present invention is that the device is
highly durable and will not degrade with repeated impact.
Yet another advantage of the present invention is that the facings
of the device are flat and thus will not interfere with the flight
of a struck ball.
A still further advantage of the present invention is that the
thermoplastic material used in making the device, the use of
encapsulated air and the addition of perforations in the facing
material in an alternative embodiment all contribute to the light
weight of the device.
These and other objects and advantages of the present invention
will no doubt become apparent to those skilled in the art after
having read the following detailed description of the preferred
embodiment which is contained in and illustrated by the various
drawing figures.
IN THE DRAWING
FIG. 1a is a perspective view of a honeycomb structure from which a
vibration dampening device in accordance with the present invention
may be severed, with the top facing partially broken away to better
illustrate the honeycomb core.
FIG. 1b is a perspective view showing the severed dampening
device.
FIG. 1c is an elevational view showing the dampening device of FIG.
1b as viewed from along the line 1c-1c of FIG. 1b.
FIGS. 2a and 2b illustrate the preferred areas of placement of the
present invention on the interwoven string diaphragm of a game
racket.
FIGS. 3a and 3b are enlarged, partially broken perspective views of
a game racket showing how the device of the present invention holds
itself in place between the strings of a game racket.
FIG. 4 illustrates how a strip of flexible honeycomb may be placed
between the strings of tennis racket.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1a illustrates a preferred embodiment of a vibration dampening
device 10 in accordance with the present invention. The stock 10
that the device 11 is cut from includes a block of
honeycomb-structured core 12 made of vibration absorbing
thermoplastic material that is bonded to and sandwiched between two
thermoplastic facings 14 and 16.
The honeycomb core 12 is made from sheets of an advanced grade
thermoplastic elastomeric material that are compression bonded
together at intermittently spaced intervals staggered between
alternate sheets. This pattern of bonding creates a honeycomb
network of elongated, generally hexagonally shaped cells when the
bonded stack of sheets is expanded.
Each cell 18 of the honeycomb core 12 is defined by four generally
S-shaped wall segments, each of which is shared by an adjacent
cell. The wall segments of each cell 18 include single thickness
wall portions 19 and double thickness wall portions 20 and 22, the
latter portions being disposed on each side of the cell where the
side wall of one cell is compression bonded to the side wall of an
immediately adjacent cell.
The upper and lower extremities of the walls forming the several
cells are deformed during a planarization operation disclosed in
our copending U.S. patent application Ser. No. 07/446,320 (now U.S.
Pat. No. 5,039,567) filed Dec. 4, 1989 and create upper and lower
surfaces 25 and 27 of the honeycomb core. Facings 14 and 16, made
from a resilient thermoplastic material, are then compression
bonded to the top and bottom surfaces 25 and 27 while the core is
held in an expanded configuration. The addition of the facings
encapsulates air within each cell and enhances the device's
spring-back characteristics. The device's superior shock absorption
characteristics result in part from the use of thermoplastic (or
thermoplastic elastomeric materials) for both the honeycomb core 12
and the facings 14 and 16. In addition to their shook absorption
qualities, these materials are tear resistant and highly resilient,
yet extremely light weight so that the balance of the racket face
is not affected by the insertion of one or more devices between the
strings of a game racket.
FIG. 1b illustrates a device 11 in accordance with the present
invention that has been severed from the honeycomb structure of
FIG. 1a. The device 11 is cut from the stock 10 in a pattern that
will expose the walls of the cut cells at the sides of the device.
In other words, when a cut is made in a direction normal to the
direction of the double thickness wall portions 20 and 22 (the x
direction in FIG. 1b), it is made along the midline of each cell
18. Similarly, when a cut is made parallel to the direction of the
double thickness wall portions 20 and 22 (the y direction in FIG.
1b), severance is made through the cell 18 on either side of the
double thickness wall portions, between the side of the cell 18 and
the midline of the cell 18.
FIG. 1c is a side view of the device 11 illustrated in FIG. 1b,
taken along the line 1c-1c of FIG. 1b, and showing how the device
11 conforms to the cylindrical shape of a string 15 and 17 when
inserted in place in a game racket. The width of the device 11 is
slightly larger than the distance between the two parallel strings
15 and 17 so that, when the device 11 is inserted between the
strings, the strings squeeze the sides of the device 11. The
exposed flexible honeycomb core 12 at the sides of the device will
buckle and conform to the shape of the strings 15 and 17. The
dashed lines in FIG. 1c show how the side walls buckle around a
string 15 and 17, forcing the facings 14 and 16 to bend toward each
other. The buckled walls and facings grip the string and aid in
holding the device 11 in place.
The vibration absorbing effectiveness of the device 11 is most
prominent when the device 11 is placed at the extreme top, bottom
or either side of the racket face, between the racket frame and
first string of the interwoven string diaphragm. Within these
quadrants, the device 11 would be inserted between two parallel
strings that are woven in a direction perpendicular to a first
string. FIG. 2a illustrates the head of a racket 24 with a device
11 inserted at the bottom of the racket face between the frame 26
and the first laterally extending string 28 and between the two
centermost longitudinally extending strings 30 and 32 running
perpendicular to the string 28. An alternative placement of the
device is illustrated in dashed lines 34 at the top of the racket
face between two parallel strings 36 and 38 that are not the two
centermost strings.
Similarly, FIG. 2b shows a racket head 24 with the device 11 of the
present invention placed in the area to the left side of the racket
face. Additionally, an alternately positioned device at the right
side of the racket face is shown by the dashed lines 40. Multiple
devices can be used, if the player desires, and can be placed in
any suitable combination as illustrated in FIGS. 2a and 2b.
FIGS. 3a and 3b are elongated views showing a device 11 inserted
between the frame 26 and the interwoven string diaphragm of a game
racket. In FIG. 3a, the top facing 42 of the device is shown
partially broken away to better illustrate how the walls of the
cells along the sides of the device conform to the two parallel
strings 30 and 32 to hold the device 11 in place. Note that the
facings 42 and 44 cover the top and bottom surfaces of the
honeycomb core 12, but along the sides of the device 11, the
flexible honeycomb core 12 is exposed. When the device 11 is
inserted between two parallel strings 30 and 32 of the racket, the
strings slightly squeeze the device 11 at its sides because the
width of the device is a bit larger than the separation between the
strings. As a result of this squeezing, the open cell walls at the
sides of the device 11 conform to the cylindrical shape of the
strings and generally wrap around portions of the strings.
FIG. 3b illustrates the same device 11 as that in FIG. 3a without
the facing broken away. Because the facings 42 and 44 of the device
11 are fusion bonded to the top and bottom of the honeycomb core,
the facing edges along the sides of the device that interface with
the strings will be slightly deformed toward each other when the
device in inserted between the strings. The facings are pulled
inwardly because the cell walls of the honeycomb core buckle and
wrap around the string. This is shown in FIG. 3b by the gathers in
the facing along the engaging edges of the device 11.
Alternately, the device may be inserted in such a way as to engage
not only the two parallel strings, but also the first transverse
string from the frame of the racket. Additional vibration reduction
may be experienced with this disposition.
The rectangular shape of the device described thus far is for
purposes of illustration only. A device in accordance with the
present invention can be of any configuration, including but not
limited to square, circular, or octagonal.
An alternate embodiment of the present invention provides an
example of use of a differently shaped piece of flexible honeycomb.
FIG. 4 shows how a thin strip 46 of flexible honeycomb can be woven
through a section of the string diaphragm of a tennis racket to
dampen string vibrations. The strip 46 is held in place in the same
manner as the block of honeycomb previously illustrated in the
preferred embodiment. The exposed walls of the cut cells at the
sides 48 and 50 buckle and conform to the shape of the strings 52
and 54 that are engaged by the strip 46.
Although the present invention has been described above in terms of
a specific embodiment, it is anticipated that alterations and
modifications thereof will no doubt become apparent to those
skilled in the art. It is therefore intended that the following
claims be interpreted as covering all such alterations and
modifications as fall within the true spirit and scope of the
invention.
* * * * *